A heat exchanger is an apparatus which is disposed between heat exchanging medium flowing therethrough and external environment and absorbs heat from one and discharges the heat to the other. The heat exchanger includes a first header tank and a second header tank spaced apart from each other by a predetermined distance and disposed parallel to each other; an inlet pipe and an outlet pipe formed in the first header tank or the second header tank; a plurality of tubes, each tube being fixed by the pair of the header tanks at both ends thereof to form a passage for heat exchanging medium; and a plurality of fins interposed between the tubes.
An inside of the header tank is formed with a partition wall for partitioning compartments, and various heat changing medium passages are formed using a baffle.
Also, the header tank may be manufactured by various methods including use of an extrusion pipe, folding of a plate, or mixing of the two methods.
FIG. 1 illustrates various conventional header tank structures in which two plates are joined to form the partition wall. FIG. 1(A) illustrates a header tank structure disclosed in Japanese published patent application No. 2004-044920, FIG. 1(B) Japanese published patent application No. 1998-019490, FIG. 1(C) Japanese published patent application No. 1995-318288, and FIG. 1(D) Japanese published patent application No. 1993-001896. In FIG. 1, insides of dotted ellipses indicate partition walls.
More specifically, FIG. 1(A) shows a header tank 10 in which a constitution 1 which constitutes an upper face of the header tank 10 and a constitution 2 which constitutes a lower face and two side faces and is integrally formed with the partition wall are coupled; FIGS. 1(B) and 1(C) show a header tank 10 in which a single plate is folded and a partition wall 11 is integrally formed; and FIG. 1(D) shows a header tank 10 in which side faces of reverse ‘U’ shaped members, each forming a compartment, are joined to form the partition wall 11 and a header formed with a tube inserting hole is coupled to form the header tank 10.
However, as shown in FIG. 1, various problems are generated when the partition wall is formed by coupling of two plates.
In general, in order to couple the two plates, flux is applied between two plates and the two plates are then brazed. However, since it is hard to remove foreign substances in the case that the foreign substances such as oil and air are mixed between the two plates, a space may be generated between the plates.
Also, since the partition wall is formed long in a rectangular shape in a longitudinal direction of the header tank, a face to be brazed is very wide. Therefore, flow of the flux is not smooth and thus joining force is not uniformly applied.
In addition, in the case that the joining area is wide, air between the faces to be joined cannot be discharged to the outside and is remained between the faces to be joined. This also results in brazing defect.
In other words, the conventional heat exchanger has a problem that the foreign substances such as oil and air cannot be easily moved and the joining force cannot be uniformly formed and thus durability of the heat exchanger is lowered when the partition wall is formed by joining of two plates.